This invention relates to ejection seats for aircraft.
During ejection from an aircraft, the head may be thrown forward and downward, sometimes causing severe or fatal posterior spinal column, and/or posterior spinal cord injury to the ejected aircrewman.
To prevent injury to the body, arms, and legs, restraint systems have been devised for use with ejection seats. To prevent injury to the head and neck, the ejection handle was placed over the head and attached to a face curtain, which was pulled downward to cover the face during ejection from the aircraft.
With recent aircraft improvements in altitude and maximum speed of aircraft operation, the need for more positive head restraint has been indicated. Various inventions to prevent head and neck injury have been devised, for example, in the Martin-Baker Aircraft Co., Ltd. U.K. Pat. Nos. 583,257, and 1,012,355. These United Kingdom patents were also taken out in the United States, France, Switzerland, and Sweden. The U.K. Pat. No. 1,012,355 involved:
"head-restraining equipment for an aircraft ejection seat including a head rest, comprising: a retraction mechanism adapted to be mounted on the seat; such retraction mechanism including a rotatable reel for a flexible member adapted to connect said mechanism to the head of an airman in an ejection seat; said retraction mechanism being operative to apply tension to said flexible member to draw the airman's head against said head rest: means being provided to permit actuation of the mechanism by fluid pressure if desired; and means operative subsequently to operation of said retraction mechanism for disabling the connection between the retraction mechanism and the seat occupant's head."
The above head restraint invention, and others, were subsequently abandoned or did not become accepted for various reasons, including problems with helmet retention and cumbersomeness.
In some restraining systems, inertial reel systems are coupled from the seat (ejection or otherwise) to different portions of the helmet. For example, in Lindstrom U.S. Pat. No. 2,638,293, the inertial reel connection is made to the top of the helmet and two additional connections are made to the sides of the helmet. When the connection is made to the top of the helmet, it is possible for relative neck angulation movement to occur between the head of the user and his torso or body which exposes the neck to serious and possibly lethal injury; said connections to the helmet impose undesirable lateral restraint on head movements of the pilot during normal flight operations. Those prior head restraint systems which are effective, impose such constraints on head movement during normal aircraft or vehicle operation as to place their acceptance and use on a relatively low level. In Forman U.S. Pat. No. 3,645,480, a magnetic force is suggested to restrain the head, but this system requires the pilot voluntarily positioning his head in proximity to the electromagnet and in uncontrolled situations, high G forces may well preclude such voluntary positioning on the part of the pilot.
This invention relates to an improved head and neck restraint system for protecting the head, neck, spinal column, and spinal cord from injuries resulting from rapid forward-downward head movements, and from rapid side-to-side head movements, which may occur during high speed ejection from modern aircraft or during automobile crashes involving sudden stop of the vehicle. All previous inventions described the basic mechanism for head-neck restraint but did not provide for a workable restraint system involving helmet, seat-back position, head, and neck: because they were inadequate, all previous head-neck restraint systems have been seldom used.
The main lethal injury from inadequate head and neck restraint during automobile crashes and high speed ejection from aircraft is spinal cord contusion subsequent to rupture of posterior interspinous ligaments of the spinal column, especially the posterior atlanto-occipital (C1-OCC) and posterior atlanto-axial (C1-C2) membranes. The fatal spinal cord injury results from the sudden uncontrolled forward and downward movement of the head, on the neck which is restrained by a shoulder harness restraint system present in aircraft and race cars.
The prevention of fatal neck injuries in race cars and military aircraft ejection seats requires a head and neck restraint system which will compliment the present existing shoulder restraint system, and not produce further injury to the head and neck.
The invention here described relates to an improved head and neck restraint system for protecting the neck and cervical spinal cord from injuries resulting from rapid forward decleration and during ejection from military aircraft. In rapid forward decleration, the head is thrown forward with the shoulders held in site by the shoulder harness system; in ejection upward during emergency escape from a military aircraft, the pilot's body accelerates upward, throwing the head forward and downward, producing posterior neck and cervical spinal cord injury. In each case, the shoulder restraint system augments the uncontrolled forward-downward movement of the head on the neck, producing neck injury.
The present invention relates generally to protective apparatus for protecting the neck of humans, particularly military aircraft pilots and race car drivers, from posterior neck and spinal cord injuries resulting from rapid forward decleration, or rapid upward acceleration.
At relatively low G forces (20 to 30 G) and low speeds (50 to 60 mph), pilots and race car drivers are exposed to potentially lethal cervical spinal cord injury, which may cause a rupture of the posterior atlanto-occipital (C1-OCC) or posterior atlanto-axial (C1-C2) membranes of the cervical spinal cord, with or without subsequent spinal cord contusion. Such lethal injury occurs in military aircraft accidents, during military ejection seat use in high performance aircraft, and in high speed race car crashes, where the shoulders are restrained by seat and shoulder harnesses but the head is unrestrained, and the resultant restraint system is ineffective for preventing injury to the posterior atlanto-occipital/atlanto-axial membranes and spinal cord.
In some recent inventions of restraint systems, inertial reel systems are connected from the seat (ejection or otherwise) to different positions of the helmet. For example, in Martin-Baker U.K. Pat. No. 1,012,355 the inertial reel connection is made to the lower back of the helmet; in Lindstrom U.S. Pat. No. 2,638,963, the inertial reel connection is made to the top and sides of the helmet; in Forman U.S. Pat. No. 3,645,480, the helmet restraint is by a magnetic force which becomes operative when the ejection seat is activated with the pilot placing the helmet against the seat-back magnet site. In these previous inventions, no teaching as to the exact site and strength of restraint was made; no teaching was made as to helmet requirements to prevent movement or exit of the head from the helmet; no specification as to helmet design was made so as to prevent anterior garroting of the pilot if the helmet restraint was operated as designed.
The present invention of an improved head and neck restraint system specifies (1) the site of helmet attachment, (2) the site of seat-back inertial reel adjustment, and, (3) the site of certain helmet design improvements to prevent garroting anterior neck injury and the loss of the helmet during use of the head and neck restraint system.
According to the present invention, an inertial reel connection to the helmet is made above the level of the superior nuchal line of the posterior skull without restricting normal head movements and side vision. To accommodate different size users, the helmet attachment site is chosen for each individual with the helmet in place. The seat-back attachment is height adjustable, so as to assure that the connection to the inertial reel actuator device is along a line such that forward momentum of the user's head transmits a reaction force via the forehead and chin engagements of the user, to the helmet forehead pad and chin strap; through a vector substantially aligned with the superior nuchal line of the user's skull, above the posterior cervical vertebrae. Thus, the restraint is along a reaction line passing through a small zone located at the lower posterior central area of the back of the user's head, said reaction line being substantially perpendicular to the axial line of the vertebrae-skull in the normal erect posture of the user.